The invention relates generally to a method of treating a polymer to increase its dielectric properties, and to an article comprising a layer of the treated polymer.
Polymers with high resistivity, high permittivity, low dissipation factors and high electric field breakdown strengths (Vb) have important applications as dielectrics in electronic devices, such as a capacitor. The electronic industry is cost- and performance-driven, and constantly increasing demands are made on materials to lower cost, and improve their reliability and performance. Polymer based devices have long been of interest because manufacturing technologies associated with extrusion or solution casting of polymer films can be readily combined with thin film metallization techniques, to yield devices that are flexible and economical, and which can be manufactured into very large electronic devices.
Polymer films such as polycarbonate, polypropylene and polyester have been the insulating media of choice for fabrication of thin film electrostatic capacitors for operation in the kilovolt range. Polymer based capacitors have been the capacitor of choice for many power electronics and pulse power applications, because of their inherent low dielectric losses, excellent high frequency response, low dissipation factor (DF), low equivalent series resistance (ESR), and high voltage capabilities. Polymer based capacitors have no capacitance coefficient with applied voltage, and metallic migration or leaching does not occur, as observed in the case of ceramic based capacitors.
Over the last decade, significant increases in capacitor reliability have been achieved through a combination of advanced manufacturing techniques and new materials. In addition, polymer-based electronic devices, such as a capacitor, would offer compact capacitor structure, self-clearing capability, longer lifetime, and higher energy density. These advantages, coupled with the advantage of reduced size, simplicity, and cost of manufacturing, enable the wide use of these polymer based capacitors in the power electronics industry.
Polymer based capacitors are lightweight and compact and, hence, are attractive for various land based and space applications. However, most of the dielectric polymers are characterized by low energy densities (<5 J/cc), and/or have low breakdown strength (<450 kV/mm), which may limit the operating voltage of the capacitor. Other disadvantages are sometimes associated with these types of capacitors as well, relating to thermal stability and reduced lifetime, for example. In order to achieve high energy density, it may be desirable to have both high dielectric constant and high breakdown strength. A trade-off between these two properties may not be advantageous. Most dielectric polymers that exhibit high breakdown strength have a relatively low dielectric constant.
Therefore, it is important to identify a material with a considerably high dielectric constant and relatively high breakdown strength. There is a need for polymer materials that would address the aforementioned problems and meet the current demands of electronics industry applications. Further, there is a need for simpler and versatile methods to prepare high quality polymer materials for use in polymer based electronic devices.